My previous work has provided evidence suggesting that the lipid composition of the platelet is determined during the development of the parent cell, the megakaryocyte and disorders on platelet function occur because of disturbances in megakaryocyte development. The effects on megakaryocyte and platelet lipid metabolism of three disorders thought to alter platelet function will be studied. (1) Hypercholesterolemia: The source of megakaryocyte and platelet cholesterol content will be studied. The relative contributions of cholesterol synthesis in the megakaryocyte, uptake of plasma cholesterol by the megakaryocyte, and uptake of cholesterol of platelets of cell membranes will be assessed. The cells will be labeled by feeding quinea pigs [3H]cholesterol and radiolabeled cholesterol precursors, and the localization of radiolabeled cholesterol in the cell membranes will be probed (a) kinetically, by exchange and removal of radioactive cholesterol from the cells using cholesterol acceptors as plasma and liposomes, and (b) morphologically by autoradiography. Guinea pigs will be made hypercholesterolemic by cholesterol feeding, and it will be determined whether the cells accumulate excess cholesterol and whether megakaryocyte cholesterol and phospholipid synthesis are altered. (2) Ethanol ingestion: The effect of acute and chronic ethanol intestion on guinea pig megakaryocyte morphology and lipid metabolism and platelet lipids will be determined. The contributions of ethanol itself and of plasma constituents such as abnormal lipoproteins to abnormal megakaryocyte development will be assessed. (3) Diabetes: The effect of insulin on lipid synthesis in normal megakaryocytes will be determined by studying lipid metabolism in the cells in vitro in the presence and absence of insulin. The effect of insulin deprivation in vivo on megakaryocyte and platelet development and lipid metabolism will be studied by inducing diabetes in guinea pigs with the drugs streptozotocin and diazoxide (Proglycem), and the ability of insulin to reverse these effects will be tested. These experiments should provide information concerning and importance of the megakaryocyte in determining normal platelet development and function.